Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
Notional Amount	$ 456,602	$ 388,121
Asset Derivatives
Derivative assets, gross amount offset	(233)	(283)
Derivative assets	280	202
Liability Derivatives
Derivatives liabilities at fair value	(132)	(140)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	1,900	2,900
Cash collateral received for derivative instruments	(2)	(5)
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	317,568	299,557
Asset Derivatives
Derivative assets, gross amount offset	(233)	(283)
Derivative assets	134	45
Liability Derivatives
Netting adjustment	2,154	3,200
Derivatives liabilities at fair value	(22)	(23)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	42,331	38,541
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Total risk management derivatives designated as hedging instruments | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	275,237	261,016
Asset Derivatives
Derivative assets, gross	367	328
Liability Derivatives
Derivative liabilities, gross	(2,176)	(3,223)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	18,107	9,954
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	141,966	136,648
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	24,224	28,587
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	119,680	115,288
Asset Derivatives
Derivative assets, gross	77	76
Liability Derivatives
Derivative liabilities, gross	(2,041)	(3,085)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	250
Asset Derivatives
Derivative assets, gross	54	44
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	332	316
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(55)	(66)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	7,006	5,816
Asset Derivatives
Derivative assets, gross	209	195
Liability Derivatives
Derivative liabilities, gross	(11)	(12)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	5,916	2,666
Asset Derivatives
Derivative assets, gross	27	13
Liability Derivatives
Derivative liabilities, gross	(69)	(60)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	87	32
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	109,374	60,940
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	109	112
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(99)	(104)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	3,587	2,734
Asset Derivatives
Derivative assets	5	14
Liability Derivatives
Derivatives liabilities at fair value	(6)	0
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	32,495	14,264
Asset Derivatives
Derivative assets	39	98
Liability Derivatives
Derivatives liabilities at fair value	(57)	(2)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	73,292	43,942
Asset Derivatives
Derivative assets	65	0
Liability Derivatives
Derivatives liabilities at fair value	(36)	(102)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	29,660	27,624
Asset Derivatives
Derivative assets	37	45
Liability Derivatives
Derivatives liabilities at fair value	$ (11)	$ (13)